FACTS AND FACTORS OF DEVELOPMENT 69 



and in all cases it is found that their method 

 of responding to stimuli is not at first really 

 purposive and intelligent but by the gradual 

 elimination of useless responses and the 

 preservation (or remembering) of useful ones 

 the behavior may come to be purposive and 

 intelligent. 



Thorndike found that when dogs, cats and 

 monkeys were confined in cages which could 

 be opened from the inside by turning a button, 

 or pressing upon a lever, or pulling a cord, 

 they at first clawed around all sides of the cage 

 until by chance they happened to operate the 

 mechanism which opened the door. There- 

 after they gradually learned by experience, 

 that is, by trial and error, and finally by trial 

 and success, just where and how to claw in 

 order to get out at once. When a dog has 

 learned to turn a button at once and open a 

 door we say he is intelligent, and if he can 



sponses are in the main self-preservative is due to the teleo- 

 logical organization of Paramecium which has been evolved, 

 according to current opinion, as the result of long ages of 

 the elimination of the unfit. If, in the opinion of any one, 

 the expression "trial and error" necessarily involves a striving 

 after ends, it would be advisable to replace it in this case by 

 some such term as "useful or adaptive reactions." 



